DCC Archive I did surgery on my new (old) Dynaco ST-70...

I got a Dynaco ST-70 over a month ago with Mullard tubes and yesterday I found some courage (a sip of whiskey) and installed the SDS power mod and nothing blew up!! I have next to no ability with soldering yet I've been wanting a good excuse to learn. The unit was in near mint condition when I got it and now it's in near toast condition (kidding). The bias wasn't holding properly and I was decided to do the mod. I spent several hours carefully working on the board and then stripping the old stuff out. I fired it up and all was well. The Dynaco is now holding the bias correctly and it still sounds great. Everything everybody on the boards been saying about the warmth and realism of tube gear is 1000% on the money.

Todd

 

Glad things worked out for ya Todd. Just can't wait for my Bottlehead Foreplay preamp and Paramour 2A3's to arrive.

I'm thinking about buying an ST-70 or some Mark III's once my wallet recovers from my current investment. Still second guessing myself about not driving Steve's Mark III's up further on Ebay. I wound up spending more on my single ended triodes than I would've on a non Steve Hoffman owned set of Mark III's and as was mentioned at the time, I wouldn't have to worry as much about speaker efficiency.

This is definately an evolving project.

 

I got the SDS labs power mod from Triode Electronics. The instructions for putting the board together was pretty clear but the installation and stripping of the ST-70 was pretty vague. I had to spend a lot of time figuring out which wire was what and how to extend and replace other stuff. I almost gave up 20 or so times. I had one scare when I first tested the unit. One of the output tubes plates started glowing very bright and hiss was coming out of the speaker (after 2 or 3 minutes). I pulled the plug fast and opened the unit and noticed a wire was touching a solder joint on the newly installed board (it's crammed in the bottom tightly). I corrected and made sure all the tubes were seated correctly and it's been working fine and holding the set bias. I also connected the input/output wires of the bias controls in reverse, etc. I called up Ned at Triode to discuss my fears and observations and he explained that if I installed anything incorrectly then it wouldn't be able to hold the bias, etc. The unit still sounds great and I learned a few things. I noticed my soldering skills improved with every step. I kept the old parts... I'm just happy that I faced my initial fear with this and accomplished something I never did before. The ST-70 is a very nice sounding unit and I'm enjoying my music more...

Todd

 

Drew,

Good choice on the Bottlehead gear. I've read a lot of good things about those kits. The ST-70 sounds excellent. I'm very impressed with the midrange. I'm not having any problems with muddy bass because I have it working with an M&K 125 mk II sub with a 85hz crossover... I listened to the DCC vinyl of "Nick of Time" tonight and the tubes worked well with it (sadly, the pressing is defective and I have to return it for a replacement). Let us know how the Bottlehead gear sounds when you get them running.

Todd

 

Next thing you know, you'll be building a tube amp from one of those schematics at the triode electronics page from scratch.

 

Drew,

I highly doubt it! I hate fire and smoke...

Todd

 

Actually I've been thinking about it. Wonder if I could turn it into a business.
Yeah, thats the ticket!

Unfortunately everyone I know think I nuts for forsaking solid state. Can't wait to educate them.